In recent years, photographic materials having good original reproducibility and processing systems which can reduce processing waste liquid have been desired in order to cope with the diversity and complexity of printed matter and from increasing awareness of the environment in the field of photomechanical processes.
In order to improve the reproduction of continuous-gradational halftone dot images or line images, image formation systems exhibiting ultrahigh-contrast (particularly, .gamma. is 10 or more) photographic characteristics are needed.
As methods for obtaining high-contrast photographic characteristics, lithographic development systems utilizing the so-called "infectious development effect" have been used for long. However, they have the problem that the developing solutions are unstable and hard to be used. On the other hand, U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,269,922, 4,272,606, 4,311,781, 4,332,878, 4,618,574, 4,634,661, 4,618,836 and 5,650,746 disclose systems for processing hydrazine derivative-containing silver halide photographic materials of the surface latent image type with a stable MQ or PQ developing solution having a pH of 11.0 to 12.3 to obtain ultrahigh-contrast negative images having a .gamma. value exceeding 10.
According these methods, ultrahigh-contrast and high-sensitive photographic characteristics can be obtained, and sulfites can be added in high concentration to the developing solutions. Therefore, the stability against air oxidation of the developing solutions is markedly improved, compared with the conventional lithographic developing solutions.
In the above-mentioned methods, the sulfite preservatives of high concentration make it possible to enhance the stability of the developing solutions. In order to obtain ultrahigh-contrast photographic images, however, it is necessary to use developing solutions having a relatively high pH value. Accordingly, the developing solutions are easily air oxidized, which requires that the developing solutions are replenished in large amounts. Then, attempts to realize systems for forming ultrahigh-contrast photographic images utilizing hydrazine derivatives with a developing solution of lower pH have been made.
U.S. Pat. No. 4,269,929 (corresponding to JP-A-61-267759 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")), U.S. Pat. No. 4,737,452 (corresponding to JP-A-60-179734), U.S. Pat. Nos. 5,104,769 and 4,798,780, JP-A-1-179939, JP-A-1-179940, U.S. Pat. Nos. 4,998,604 and 4,994,365 and JP-A-8-272023 disclose methods of using high-active hydrazine nucleating agents and nucleating accelerators for obtaining ultrahigh-contrast images by using a stable developing solution having a pH of less than 11.0. It is also disclosed that silver halide emulsions which has a high silver chloride content and which is chemically sensitized have high nucleating activity.
Further, hydrazine nucleating agents each having at least two hydrazine groups in a molecule are disclosed in JP-A-4-16938, JP-A-5-197091, JP-A-5-127287, JP-A-5-142688 and JP-A-6-148777.
In the methods known in the art, however, when one meter square of the silver halide photographic material is processed, the replenishing rate of the developing solution is required to be about from 150 ml to 450 ml. In these days when concern about environmental problems has been increased, a demand for waste liquid reduction is further increased, and an improvement in processing stability, particularly in the dependency of photographic sensitivity on the pH of the developing solution which comes into question in the hydrazine nucleating system has been strongly desired.
Further, there is also a problem such that when the high-active hydrazine nucleating agent as described above is used, sand-like fog called black peppers are readily caused in undeveloped areas.
On the other hand, a need for photographic materials for scanner output has bee growing year by year, and it has been desired to satisfy both requirements for good definition (on/off) of edge portions of images and for reduced processing unevenness (density unevenness remarkably observed in case where the output is performed for wide area at uniform dot percent). That is, there has been the dilemma that the definition of edge portions of images can be improved by enlargement of the images by nucleating infectious development, but such a photographic material with enlarged images tends to cause the processing unevenness.
With respect to photographic materials for daylight dot to dot work, there is a problem that nucleating development is quite hard to take place because of a reduction in sensitivity of the emulsion used in the system. Accordingly, the development of a technique to make the contrast higher even using a low-pH developing solution has been desired.
Hydrazine nucleating agents each having two or more hydrazide groups in a molecule are disclosed in JP-A-4-16938, JP-A-5-197091, JP-A-5-127287, JP-A-5-142688 and JP-A-6-148777. However, the above described problems are not solved yet.